[Solved] Auto-build COB lamp - less watt then calculated?

[Colpevole]

Hello,
i'm a new user, i the last months i have read a lot of tutorial and precious info on this website, and i have decided to build my own cob lamp with these components:

4x Luminus CXM-22-30-90-54-AC30-F4-3 3000k
1x Luminus CXM-22-40-80-54-AC30-F4-3 4000k

i have used cob-led-driver-selection-tool on this website for select proper power supply unit:

Two of those COBs are drived with HLG-120H-C1400B LED DRVR CC AC/DC 54-108V 1.4A
Three of those COBs are drived with HLG-240H-C1400B LED DRVR CC AC/DC 89-179V 1.4A

on both power supply i have installed a 100k ohm linear potentiometer.

Now is all ready and work but there is a problem.
With cob-led-driver-selection-tool if i select 5x CXM22 powered at 1400mA i expect to get 480W (max).

i have installed a current meter (you can read Watt, Amps in real time) on my current plug in order to verify, but maxiumum power is 190W. obviusly with 100% dimmer on each power supply.

what is wrong?

thanks for help.

[DaveJonesFan]

Hey. Looks like you've got a sensible set up. The drivers should be able to effectively run the COBs as described if they are in series circuits. Have you wired them up this way? Double check that part.

Do you have both drivers run in parallel to the AC mains through one power plug, that you are then taking your kill-a-watt style readings from to get the 190w wall draw number? Or only 1 driver plugged in at a time?

The total wattage I would expect with this setup is closer to 360w at the COBs, so a little more than that at the wall with both drivers humming. Don't think you will get to the 480w number with this setup, though.

Your HLG-120H-C1400B with 2 COBs would be 51V each * 1400mA for 71.4 watts per COB, 142.8 watts total power on that driver.

Your HLG-240H-C1400B with 3 COBs would be 214.2 watts total power on that driver, similarly.

If you have a cheap 100K ohm pot, they are known to not always reach fully 100K ohms. If you have a 10% toleranced unit and it only goes to 90% on the driver that is a scenario where I can almost see the 190w number making sense for that one driver, but it's still a bit under, so hard to say exactly what it going on from here with current info.

[Colpevole]

Hi Dave,
first of all thanks for your reply.

COB are wired in series on both of power supply, i'll check again but i'm pretty sure.

Each power supply HLG-120H and HLG-240H have his own socket, and both are connected to one of this (i don't know right term in english sorry) then to the wall.

The total wattage I would expect with this setup is closer to 360w at the COBs, so a little more than that at the wall with both drivers humming. Don't think you will get to the 480w number with this setup, though.

Your HLG-120H-C1400B with 2 COBs would be 51V each * 1400mA for 71.4 watts per COB, 142.8 watts total power on that driver.

Your HLG-240H-C1400B with 3 COBs would be 214.2 watts total power on that driver, similarly.

ok thats sound good for me, my goal was 75W for each COB in order to have a good efficence.
So total power around 360W is ok , but now i'm very far from this target


potentiometer was purchesed on amazon, i don't think is something special...

if i don't use potentiometer, this kind of power supply give me max vout? if yes i can try to remove it.

and this is what i use for measure.

thanks

[DaveJonesFan]

If you remove the pots and cap off each end of the leads individually you should have it running at 100% on the drivers that way, yes. You could try that and double check all the series wiring is done sound. Did you notice if all the cobs light up for instance? Sometimes wiring one in backwards in the series will allow some to light and not others. What else can I think of? Maybe try each driver on the watt meter individually to see how each configuration is running independently for now also. It may be one of the drivers is faulty and not reaching the right current, but this is rare.

[Colpevole]

all light turn on at same time without delay, and bright appear the same on all 5 cobs.
this evening i'll double check series connection and try with ohmmeter both potentiometer, then try individually each driver on watt meter, measure Volt out with multimeter on each power supply and i'll report result here.
thanks for support

[LEDG]

The 480W number you see in the calculator is the max power of that driver. The calculated power for your COBs is in the top right box, which is about 375W.

[Colpevole]

The 480W number you see in the calculator is the max power of that driver. The calculated power for your COBs is in the top right box, which is about 375W.

yes i undestard, and 370W is my goal from beginning.
but now i have less then 200W and i don't know why..

[bvolt]

Hey. Looks like you've got a sensible set up. The drivers should be able to effectively run the COBs as described if they are in series circuits. Have you wired them up this way? Double check that part.

Do you have both drivers run in parallel to the AC mains through one power plug, that you are then taking your kill-a-watt style readings from to get the 190w wall draw number? Or only 1 driver plugged in at a time?

The total wattage I would expect with this setup is closer to 360w at the COBs, so a little more than that at the wall with both drivers humming. Don't think you will get to the 480w number with this setup, though.

Your HLG-120H-C1400B with 2 COBs would be 51V each * 1400mA for 71.4 watts per COB, 142.8 watts total power on that driver.

Your HLG-240H-C1400B with 3 COBs would be 214.2 watts total power on that driver, similarly.

If you have a cheap 100K ohm pot, they are known to not always reach fully 100K ohms. If you have a 10% toleranced unit and it only goes to 90% on the driver that is a scenario where I can almost see the 190w number making sense for that one driver, but it's still a bit under, so hard to say exactly what it going on from here with current info.

HLG-240 + HLG-120 = 360 Watts. I think you’re on target.

[Colpevole]

ok i have done some measure.

HLG-120H-C1400B with 2 COBs:
V-out 49,5V (Voltage still the same if put dimmer from 0% to 100% don't change Volt)
84,4W - this is power measured from plug with only this power supply connected

Your HLG-240H-C1400B with 3 COBs
V-out 48,8V (Voltage still the same if put dimmer from 0% to 100% don't change Volt)
85,6W - this is power measured from plug with only this power supply connected

i forgot to check parallel/series... later i'll check

so now i use only 170W...
it's possible this situation if i have connected in parallel?

[Kiwi_Jezza]

Something isn't right here. Are you measuring voltage across a single cob? There shouldn't be over a volt of difference at 1.4A on identical cobs. How are you measuring circuit voltage? Voltage should DEFINITELY change if you are dimming the cob. Remove that dimmer. Or measure its resistance to check it is in fact 100K. Check your circuit current to see how close they are to 1.4A also. From the numbers you have given - 2 Cobs @ 49.5v on a 1.4A driver = 138.6watts.

2 in PARALLEL is about 75watts. Plus some driver losses gives you the 85 watts you mention. My guess is you've messed up your wiring.